It is generally recognized that chewing gum that is dropped in indoor or outdoor environments gives rise to considerable nuisances and inconveniences due to fact that the dropped gum sticks firmly to e.g. street and pavement surfaces and to shoes and clothes of people being present or moving in the environments. Adding substantially to such nuisances and inconveniences is the fact that currently available chewing gum products are based on the use of elastomeric and resinous polymers of natural or synthetic origin that are substantially non-degradable in the environment.
City authorities and others being responsible for cleanliness of indoor and outdoor environments therefore have to exercise considerable efforts to remove dropped chewing gum, such efforts, however, being both costly and without satisfactory results.
There have been attempts to reduce the nuisances associated with the widespread use of chewing gum e.g. by improving cleaning methods to make them more effective with regard to removal of dropped chewing gum remnants or by incorporating anti-sticking agents into chewing gum formulations. However, none of these precautions have contributed significantly to solving the pollution problem.
Recently, it has been disclosed, e.g. in U.S. Pat. No. 5,672,367 that chewing gum may be made from certain synthetic polymers having in their polymer chains chemically unstable bonds that can be broken under the influence of light or hydrolytically into water-soluble and non-toxic components. It is mentioned in this patent that chewing gum made from such polymers that are referred to as biodegradable are degradable in the environment.
WO 01/01788 discloses ingestible and degradable chewing gum based on a gum base of enzymatically hydrolysed proteins, in particular zein.
The fact that a chewing gum base component is physically, chemically or biologically degradable, however, gives rise to product stability problems, as the degradation which it is intended should progress after chewing of the gum may occur at a significant level during storage of such degradable chewing gum products, in other words, the shelf life of chewing gum comprising, as a gum base component, a degradable polymer, may be unacceptably shortened e.g. due to moisture conditions or light. An additional significant problem associated with such degradable chewing gums is that otherwise desirable chewing gum additives such as acids, flavour and active ingredient components incorporated into a degradable chewing gum formulation may, during storage of the finished products, have a deteriorating effect on the masticatory quality and other desired properties of the chewing gum due to incipient, pre-mature degradation inadvertently caused by such additives.
It has been now been found that the above pre-chewing deteriorating effects on chewing gum comprising degradable polymers can be substantially reduced by providing the chewing gum centres with a protective outer coating. Moreover, and unexpectedly, it was found that, in spite of the more delicate nature of the degradable polymers, it was possible to subject the degradable chewing gum to conventional coating processes, implying that the chewing gum centres are contacted with moisture, essentially without detectable inadvertent degradation of the degradable gum base polymers.